Method for controlling adhesion of paper on yankee drier with polyamides and resultant products

ABSTRACT

This invention relates to a paper manufacturing process which comprises drying the formed web against a heated surface, such as present on a Yankee drier, and in particular to the improvement which comprises incorporating in said web before said drying, in an amount sufficient to achieve uniform adhesion to and release from said heated surface, a water-dispersible repulpable polyamide polyamine resin containing at least two primary amine groups and at least one secondary or tertiary amine group such as the polyamide which results from the reaction of diethylene triamine with isopthalic acid.

o S Unite States atem 51 3,640,841 Winslow et a1. Feb. 8, 1972 [54] METHOD FOR CQNTROLLING 2,071,250 2/1937 Carothers ..260/78 ADHESIQN 0F PAPER ()N Y ANKEE 2,112,540 3/1938 McAndrews. ..162/ 186 REE W T 2,130,523 9/1938 Carothers ....260/78 g i g ggsgjggggg AND 2,149,273 3/1939 Carothers..... ....260/78 3,018,214 1/1962 Waldie ..162/179 72 Inventors: Alfred Edwards Winslow, Unadilla; John 3,034,922 5/ 1962 B06 ..162/158 Calvin Spider, Sidney, both of NY.

OTHER PUBLlCATlONS [73] Assignee: The Burden Company, New York, NY. |22| Filed: Apr. 29' 969 Casey, Pulp and Paper, Vol. 11 2nd edition pg. 947 [21 1 Appl. No.: 820,306 Primary Examiner-S. Leon Bashore Assistant Examiner-Richard H. Anderson h 52 11.5.01. ..162/164, 117 155 11, 162/112, A'mmey L slgaks 162/191, 260/78 TF [57] ABSTRACT [51] Int. Cl ..D21tl 3/00, D21h 3/36 [58] Field of Search ..260/78 TF; 162/164, 168, 4, This invention relates to a P p manufacturing Process which 162/158, 117/155 U, 161 p comprises drying the formed web against a heated surface, such as present on a Yankee drier, and in particular to the im [56] References Cited provement which comprises incorporating in said web before said drying, in an amount sufficient to achieve uniform adhe- UNlTED STATES PATENTS sion to and release from said heated surface, a water-dispersible repulpable polyamide polyamine resin containing at least 1,950,351 3/1934 Clark 162/186 two Primary amine groups and at least one Secondary or tertia ry amine group such as the polyamide which results from the reaction of diethylene triamine with isopthalic acid.

9 Claims, No Drawings METHOD FOR CONTROLLING ADHESION OF PAPER ON YANKEE DRIER WITH lPOLYAMllDES AND RESULTANT PRODUCTS BACKGROUND OF THE INVENTION The manufacture of paper may be considered as comprising three chief stages; the preparing of an appropriate fiber suspension, the forming of a wet web from this suspension, and the drying of the web to a desired moisture content. While the drying is commonly effected by passing the web successively around a multiplicity of steam-heated drying rolls or cans a well-known procedure involves the replacement of all or some of the relatively small drying rolls by a single large highly polished metal drying cylinder, up to 16 feet or more in diameter, from which the dried web may be removed with the aid of a doctor blade.

For the purpose of the present application all large drying cylinders of the above-mentioned type will be designated by the generic term Yankee drier. Structurally Yankee driers may vary in many respects including width, diameter, shell thickness, metal composition and degree of plating or polish which may be applied on the inside as well as on the outer surface in order to enhance heat exchange. Drying effected on any particular Yankee drier cylinder depends upon several additional factors including the temperature and rotational speed of the cylinder and the distance over which the web is kept in contact with the cylinder. The housing for a Yankee drier usually incorporates means for exhausting the evaporated moisture.

Yankee driers are particularly appropriate for producing lightweight tissues, the lightest tissues requiring no augmented drying equipment, while heavier toweling for example, usually requires additional drying on conventional smaller drying cans or rolls.

The nature of the finished paper depends upon the mechanical forces at the locus of removal of the web from the cylinder, and also upon the angle of removal. Without a doctor blade or with doctor blade substantially tangent to the circumference of the cylinder, the paper has a smooth machineglazed finish. If the doctor blade is reversed at an angle to the tangent, the finished paper is creped and this procedure is known as creping off the Yankee drier."

In spite of the many desirable advantages which accrue in using Yankee driers, there is often much difficulty in maintaining smooth removal of the web by the doctor blade. This operation requires a delicate balance between the adhesive forces holding the web uniformly on the cylinder surface and the releasing forces applied at the source of contact with the doctor blade. Many attempts have been made to attain this needed balance but none have been entirely satisfactory.

The addition of common adhesives such as glue to the fiber suspension has been tried in combination with application of release agents to the cylinder surface, but the relative amounts of adhesive and release agent have had to be changed continually during production in order to maintain even approximately constant performance. At best, this has meant a cumbersome program of on-the-spot readjustments. At worst, this approach has led to buildup of agents on the cylinder and mechanical damage to doctor blades, causing machine downtime losses. Such losses are magnified when the agents used interfere with ease of repulping the broke. Irregular distribution of adhesive forces between web and cylinder have resulted in irregularities in structure such as that which is known as cockle, and nonuniformity in forces at the blade have resulted in nonuniformity in smoothness or degree of creping. Also, when the adhesive and release agents have comprised substances conferring softness or stiffness upon the finished paper and the respective amounts of these agents have been changed during the course of production in order to maintain mechanical control, the finished products have varied inordinately in regard to softness and/or stiffness.

SUMMARY OF THE lNVENTlON We have now found a means whereby in the manufacturing of paper comprising the step of drying the formed web against a heated surface, and particularly against the cylinder of a Yankee drier, efficient uniform adhesion to the drier surface and uniform release from said surface are promoted without the cumbersome and generally ineffective precautions required by the prior art.

In short, the present invention comprises incorporating in the web before said drying, a water-dispersible repulpable polyamide polyamine resin comprising a condensate of a polycarboxylic acid with between about 0.8 and 2.2 molar equivalents of a polyalkylene polyamine containing at least two primary amino groups and at least one secondary or tertiary amine group, said resin being used in amount sufficient to achieve uniform adhesion of said web to said cylinder and uniform release therefrom as well as uniform appearance and properties of finished paper product.

DETAILED DESCRIPTION The instant invention is particularly applicable to Yankee driers and will be described in connection therewith. I

The repulpable resin of this invention must be a polyamide polyamine formed by reacting a polycarboxylic acid with a polyalkylene polyamine. As polycarboxylic acid it is preferred to use an aromatic dicarboxylic acid such as isophthalic acid, terephthalic acid, 1,4-naphthalene dicarboxylic acid, and hydrogenated derivatives of these such as tetrahydrophthalic and hexahydrophthalic acids. Other suitable aromatic acids are diphenic acid, 4,4-diphenyl dicarboxylic acid, 4,4sulfonyl dibenzoic acid; oxydibenzoic, pheynlindane dicarboxyic, 2,5-thiophene dicarboxylic, phenylendicatic, and homophthalic acids, and hydrogenated derivatives of such homophthalic acids. Relatively small amounts of aromatic acids such as trimellitic, pryomellitic, and other acids having more than two carboxyl groups, or their anhydrides, can be used with the above acids to provide chain branching in the polyamide. It is also possible to use aliphatic dicarboxylic acids, including malonic, succinic, glutaric, adipic, trimethyladipic, suberic, azelaic, diglycollic and sebacic acids and the like, as well as alpha-unsaturated acids including itaconic acid, furmaric acid, maleic acid, citraconic acid and mesaconic acid. Also suitable are cycloaliphatic dicarboxylic acids such as camphoric acid and trans-1,2-cyclobutane dicarboxylic acid. Obviously it is possible to use mixtures of two or more different polycarboxylic acids.

The polyalkylene polyamines may be selected singly or in combination from those having two primary amino groups and at least one amino group which is either secondary or tertiary, i.e., the polyalkylene polyamine of this invention has the generic formula: H NC,,H -(NRC,.H -NH where R is either alkyl, aminoalkyl or hydrogen (x may vary from O to about 5 and n may vary from 2 to about 6). Among the commercially available amines which belong in this class are diethylene triamine, triethylene tetramine, tetraethylene pentamine, dipropylene triamine, 4-aJkyldiethylenetriamine, S-alkyldipropylenetriamine, 4,7-dialkyltriethylenetetramine, and dihexylene triamine.

ln forming the polyamide polyamine the molar ratio of polyamine to polycarboxylic acid may be between about 0.8/1 and about 2.2/1, preferably between about 1.0/1 and about 1.2/1. in addition to these chief reactants the resin cook may contain minor amounts of various modifying agents such as urea, melamine, lactams, amino acids; aliphatic, aromatic and variously mixed aliphatic-aromatic diprimary amines and polyamines having other functional groups; also minor amounts of substituted polycarboxylic acids including oxydipropionic acid, thiodipropionic acid and nitrilotriacetic acid.

While the direct condensation of a polycarboxylic acid and a polyalkylene polyamine at a temperature between about C. and about 260 C. for a period between about 0.5 to

20 hours is preferred as the method for preparing the polyamide polyamine of the instant invention, other methods which are known to the synthetic chemist could be used for preparing equivalent products. For example, in place of the free acids there might be used their respective acid halides, esters, especially methyl esters, ammonia derived amides, and anhydrides where appropriate. The diprimary amines can be used in the form of their carbonates.

A particular advantage of the resin of this invention is its repulpability. Being easily soluble in water, it does not interfere with repulping a paper which has gone into broke.

The resin of this invention contributes to the dry strength of the paper comprising it but has substantially no effect on the wet strength of the paper. In order to achieve wet strength with papers comprising the resin of this invention it is necessary to use, in addition, also conventional wet strength resins. 1n the absence of wet strength resins, but in the presence of the resin of this invention, a paper is obtained which disintegrates easily on contact with water. This is particularly valuable in the manufacture of disposable tissues such as toilet paper, facial tissues, and certain kinds of diapers and the like, where easy disposability in household or institutional plumbing is desirable.

The polyamide polyamine resin of this invention is used in amount sufficient to achieve uniform adhesion to, and release of the web from, the cylinder surface and uniform appearance and properties of the finished paper. The amount required will depend upon the nature of the fibers, upon the nature of the release agents that may be used in conjunction, and upon the operating conditions of the Yankee drier including temperature and rotational speed. This requirement may be up to about 5 percent of the dry weight of the fibrous pulp content of the paper, with satisfactory results obtained with as little as about 0.2 percent. Preferred amounts for most conditions are between about 0.2 percent to about 1.5 percent.

The resins of this invention tolerate the presence of various oillike release agents which are conventionally used to help prevent excess adhesion of the drying web to the cylinder surface and to assist in removal of the dry web onto the doctor blade.

An important advantage of polyamide polyamine resin of this invention is inherent in its cationic nature which causes it to be substantive and self-exhausting to papermaking fibers even in a diluted slurry. The resin is thus conveniently added to the fiber furnish prior to formation of the web or sheet. The self-exhausting phenomenon occurs over a wide range of pH, the advantageous effects of the resin being obtainable with slurries varying in pH from about 4 to 8.5 thus encompassing practically all paper making conditions and making unnecessary the otherwise required tedious pH adjustments and related manufacturing controls. The polyamide polyamine may be partially or completely neutralized with an organic or inorganic acid prior to its incorporation in the paper. The polyamide polyamine resin of this invention has high solubility in water after addition of acid, and in some instances prior to acidification. It therefore disperses readily enough in water to permit direct addition to papermaking fiber slurries. It is preferred, however, to dilute the resin first with acidified water and to add the dilute solution to the slurry, a procedure which facilitates uniform distribution of the resin on the fibers. The substantive nature of the resin, incidentally, also gives to it the advantage that it is substantially completely removed from the waste waters and does not contribute to stream pollution.

While the aforementioned advantages of incorporating the resin in the aqueous pulp dispersion make it our preferred method of addition, a possible alternative is to introduce the resin between the wet formed web and the smooth drying surface of the Yankee cylinder using procedures well known in the art such as spraying, dipping or padding.

Although the fibrous pulp used is normally of cellulosic origin including those of various wood pulps, cotton linters and the like, the instant invention is not to be construed as limited to such fibers. Many other inorganic or organic natural and synthetic fibers are finding exploitation for specialized purposes in the manufacturing of paper. The resin of this invention functions equally well with such specialty fibers or mixtures of such with cellulosic fibers.

As described above, the resin of the instant invention is particularly useful in the drying of a paper web directly on the machine," exploiting the high increased production speeds now permissible in a single continuous operation. However, the resin of the invention could also be used on "off the machine drying and creping installations where similar problems exist in attaining high uniformity of drying on large cylinders.

The degree of substantivity and therefore the speed of selfexhaustion is increased by increasing the degree of neutralization of the poyamide polyamine by acid. This effect is related to the conversion of amino groups to corresponding cationic ammonium groups which are more strongly attracted to the anionic surface of the fibers. For the purpose of such neutralization, any donor of hydrogen ions may be used, but it is preferred to use strong acids such as hydrochloric acid, chloroacetic acid, sulfuric acid, phosphoric acid and its acid salt. As an alternative to simple addition of acid, without departing from the spirit of this invention, the polyamide polyamine may also be treated with an alkylating or quaternizing agent, e.g., with a quantity corresponding up to 0.75 molar equivalents of the amino function in the resin. Such agents conventionally consist of lower alkyl esters or substituted alkyl esters of mineral acids such as halides, sulfates and phosphates.

Solutions containing the resins of this invention may be lightened in color, if desired, by the use of known reducing or bleaching agents such as alkali metal sulfites, bisulfites, metabisulfites, hypophosphites, and hydrosulfites, sulfur dioxide, sodium formaldehyde sulphoxylate, and formaldehyde.

Solutions of these resins may also be preserved against growth of mold and bacteria by addition of known preservatives including phenols, substituted phenols and their salts such as sodium chlorophenate and sodium pentachlorophenate, and 1-(3-chloroallyl)-3,5,7-triaza-1-azoniaadamantane chloride (Dowicil-).

The invention will be further illustrated by description in connection with the following examples of the practice of it. In these examples and elsewhere herein, the proportions are expressed as parts by weight except where specifically stated to the contrary.

EXAMPLE 1 182 parts (1.42 moles) of a commercial mixture of 35 percent diethylene triamine and 65 percent triethylene tetramine were reacted with 215 parts (1.29 moles) of a mixture of 95 percent isophthalic acid and 5 percent terephthalic acid at 179-212 C. for 5.5 hrs., collecting the liberated water through a condenser. The polyamide product was dissolved while still hot in 35 parts ethylene glycol, 101 parts of water, and 51 parts of methanol to give a solution having the following properties: viscosity (Brookfield model RVF, spindle no. 625 (3.), 51,000 c.p.s.; Sp. Gr. (25 C.). 1.17; flash point (Tag. open cup), 180 F.; solids C.), 70.3 percent; Gardner color value of 7; and acid number, 15. This resinous product is sparingly soluble in water.

To 87.1 parts of 28 percent phosphoric acid diluted with 136.6 parts of water and 24 parts of methanol were added and dissolved 88.5 parts of the previously prepared resinous solution. The pH was adjusted to a final value of 27. with reagent hydrochloric acid (diluted with an equal amount of water), and the resultant product solution gave a value for determined solids C.) of 29.8 percent. It was infinitely water dilutable, showed strong adhesion to paper and metal, and is cationic.

EXAMPLE 2 A slurry of unbleached Kraft pulp of Canadian Standard Freeness 450 was adjusted to a pH of 8.0 with sodium bicarbonate. A portion of the acidified resin of example 1 was diluted to 2.5 percent solids and added to the slurry in proportion to correspond to a level of 0.62 percent on a bone-dry pulp solids basis. Aliquots of the treated pulp slurry each corresponding to 5 grams of bone-dry pulp, were used to make handsheets (8X8 inches) on a Noble and Wood sheet machine. Four sheets thus prepared were drum-dried on the machine, corresponding to off-machine commercial conditions. Two strips from each sheet were subsequently dried for an hour at 220 F. to represent maximum cure.

For comparison a second series of four sheets was likewise prepared from untreated pulp slurry not containing the resin of this invention.

All the sheets were conditioned overnight at 50 percent R.l-l. and 73 F. Standard wet-strength tests were made after 10-minute soaks in water. Two measurements of tensile strength were made on each of the sheets, providing eight measurements corresponding to each type of preparation.

In case of the machine-cured sheets, those containing the resin of this invention had an average wet strength equal to 0.7 lbs. per mm. width, as compared to 0.6 lbs. for the comparison sample containing no additive.

In case of the samples which had the additional cure at 220 F., the resin-treated and untreated speciments had wet strengths respectively equal to 1.4 and 1.2 lbs. per 15 mm. width. Thus it is apparent that the resin of this invention has substantially no effect as a wet-strength resin when applied at a level which in the case of commercial wet-strength resins is sufficient to increase the wet strength by a factor of several fold.

EXAMPLE 3 Diethylenetriamine 112 parts (1.09 moles) and water 100 parts were placed in a vessel equipped with mechanical agitator and condenser. into this solution was introduced itaconic acid 129 parts (0.99 mole). This corresponds to 1.10 moles of diethylene triarnine for 1 mole of the acid. After the acid had dissolved in the amine solution, the resulting mixture was heated gradually up to the temperature of l00l 10 C. and water was boiled off.

The heating was continued until the temperature rose to l60-165 C. The temperature was maintained for 3 hours until the amine salt which had been formed in the initial reaction was decomposed to the polyamide product. This was then cooled to about 140 C. and dissolved in 200 parts of water. The viscosity as measured at a temperature of 23 C. in a solution of solids content about 50 percent was then F on the Gardner scale.

EXAMPLE 4 A typical sulfite pulp furnish is formed on a Fourdrinier paper machine into a tissue web having a basis weight of about 10 pounds per ream (3000 square feet) on a bone-dry basis. The formed wet tissue is carried on felt from the forming wire and through the main press. it is then sprayed with an aqueous solution of the polyamide product of example 1, acidified as therein, in a manner such as to obtain a uniform distribution on the web corresponding to about 0.45 percent on a bone-dry pulp basis. The thus-treated tissue web is then conveyed by a top felt into a pressure nip between a large Yankee drying cylinder and an associated press roll. The web is dried to a standard moisture content and creped off the surface of the drying cylinder with a standard creping doctor blade continuously yielding a high grade of uniformly creped tissue without cockling, in strong contrast to the results when corresponding pulp is run in the absence of the polyamide of this invention,

characterized by cockling of the drying paper on the cylinder surface and nonunifonn creping to a product with large portions which are unsi htl and unacce table.

The tissue treate wit the resin 0 this invention is superior to untreated tissue also in its performance during rewinding, showing a much lower incidence of tearing of the web. Furthermore the treated finished expanded dry creped tissue web is very satisfactory, being very soft and limp as required.

EXAMPLE 5 EXAMPLE 6 The procedures of example 4 and 5 are repeated with the product of example 3, acidified as in example 1. The advantages of processing and products obtained in examples 4 and 5 repeated.

it will be understood that it is intended to cover all changes and modifications of the examples of the invention herein chosen for the purpose of illustration which do not constitute departures from the spirit and scope of the invention.

What is claimed is:

1. in a paper manufacturing process which comprises dispersing fibrous pulp in water, forming a continuous web from the pulp dispersion and drying the formed web against a heated surface, the improvement which comprises incorporating in said web before said drying, a water-dispersible repulpable resin in amount sufficientto achieve uniform adhesion to and release from said heated surface, said resin comprising a condensate of a polycarboxylic acid with between about 0.8 and 2.2 molar equivalents of a polyalkylene polyamine containing at least two primary amine groups and at least one secondary or tertiary amine group.

2. The improvement of claim 1 wherein the repulpable resin is incorporated in the pulp dispersion.

3. The improvement of claim 1 wherein the polycarboxylic acid is selected from the group consisting of isophthalic acid, terephthalic acid, and mixtures thereof and the polyalkylene polyamine is selected from the group consisting of diethylene triamine, triethylene tetramine and mixtures thereof.

4. The improvement of claim 1 wherein the polycarboxylic acid is itaconic acid and the polyalkylene polyamine is diethylene triamine.

5. The improvement of claim 1 wherein the amount of resin incorporated is from about 0.2 percent to about 5 percent of the dry weight of the fibrous pulp and the heated surface is a Yankee drier.

6. The improvement of claim 3 wherein the amount of resin incorporated is from about 0.2 percent to about 5 percent of the dry weight of the fibrous pulp.

7. A papermaking slurry comprising a fibrous papermaking pulp and from about 0.2 percent to about 5, based on the dry weight of the fibrous pulp, of a water-dispersible repulpable resin comprising a condensate of a polycarboxylic acid with between about 0.8 and 2.2 molar equivalents of a polyalkylene polyamine containing at least two primary amine groups and at least one secondary or tertiary amine groups.

8. A fibrous paper web comprising a fibrous pulp and between about 0.2 percent and 5 percent, on a dry weight basis, of a condensate of a polycarboxylic acid with between about 0.8 and 2.2 molar equivalents of a polyalkylene polyamine containing at least two primary amine groups and at least one secondary or tertiary amine groups.

9. The process of claim 1 wherein the resin is neutralized with an acid. 

2. The improvement of claim 1 wherein the repulpable resin is incorporated in the pulp dispersion.
 3. The improvement of claim 1 wherein the polycarboxylic acid is selected from the group consisting of isophthalic acid, terephthalic acid, and mixtures thereof and the polyalkylene polyamine is selected from the group consisting of diethylene triamine, triethylene tetramine and mixtures thereof.
 4. The improvement of claim 1 wherein the polycarboxylic acid is itaconic acid and the polyalkylene polyamine is diethylene triamine.
 5. The improvement of claim 1 wherein the amount of resin incorporated is from about 0.2 percent to about 5 percent of the dry weight of the fibrous pulp and the heated surface is a Yankee drier.
 6. The improvement of claim 3 wherein the amount of resin incorporated is from about 0.2 percent to about 5 percent of the dry weight of the fibrous pulp.
 7. A paper-making slurry comprising a fibrous paper-making pulp and from about 0.2 percent to about 5 percent, based on the dry weight of the fibrous pulp, of a water-dispersible repulpable resin comprising a condensate of a polycarboxylic acid with between about 0.8 and 2.2 molar equivalents of a polyalkylene polyamine containing at least two primary amine groups and at least one secondary or tertiary amine groups.
 8. A fibrous paper web comprising a fibrous pulp and between about 0.2 percent and 5 percent, on a dry weight basis, of a condensate of a polycarboxylic acid with between about 0.8 and 2.2 molar equivalents of a polyalkylene polyamine containing at least two primary amine groups and at least one secondary or tertiary amine groups.
 9. The process of claim 1 wherein the resin is neutralized with an acid. 